Wednesday, June 18, 2014

New paper finds global annual precipitation has increased 0.34 inches per year since 1900

A paper published today in the Journal of Atmospheric Sciences finds global average annual precipitation has slightly increased by 0.34 inches per yearover the past 111 years.

According to the authors,

"Our reconstructed time series of the global average annual precipitation shows a 0.024 (mm/day)/100 year trend"

which is equivalent to 0.000944882 inches per day or 0.34 inches per year.

Where is the evidence that this slight increase in global precipitation over the past 111 years is causing droughts or a global climate catastrophe? Most likely, it has contributed along with CO2 fertilization and warming to the greening of the planet.

Department of Mathematics and Statistics, San Diego State University, San Diego, CA 92182, USA

Thomas M.Smith

NOAA/NESDIS/STAR and ESSIC/CICS, University of Maryland, College Park, MD 20740, USA

Phillip A.Arkin

ESSIC/CICS, University of Maryland, College Park, MD 20740, USA

Abstract

This paper provides a multivariate regression method to estimate the sampling errors of the annual quasi-global (75°S, 75°N) precipitation reconstructed by an empirical orthogonal function (EOF) expansion. The Global Precipitation Climatology Project (GPCP) precipitation data from 1979-2008 are used to calculate the empirical orthogonal functions (EOFs). The Global Historical Climatology Network (GHCN) gridded data (1900-2011) are used to calculate the regression coefficients for reconstructions. The sampling errors of the reconstruction are analyzed in detail for different EOF modes. Our reconstructed time series of the global average annual precipitation shows a 0.024 (mm/day)/100a trend, which is very close to the trend derived from the mean of 25 models of the Coupled Model Intercomparison Project Phase 5. Our reconstruction examples of 1983 El Niño precipitation and 1917 La Niña precipitation demonstrate that the El Niño and La Niña precipitation patterns are well reflected in the first two EOFs. Although our validation in the GPCP period shows remarkable skill at predicting oceanic precipitation from land stations, our error pattern analysis through comparison between reconstruction and GHCN suggests the critical importance of improving oceanic measurement of precipitation.